Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

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Recently, when I tested my Git Over HTTP server, I found a bug in Git. When we used git -c protocol.version=2 clone --shallow-since , if the time format is wrong, it will cause git to wait indefinitely.

Github supports Wire Protocol to reproduce, Gitlab does not support it and does not reproduce it.

The commands that can be retried are as follows:

```shell
# time format wrong
git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
# trace
GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
```
We can see that the server closes the HTTP connection after sending the `shallow-info\n` message, and git-remote-http(s) is still waiting.

```
$ git --version --build-options
git version 2.24.0
cpu: x86_64
no commit associated with this build
sizeof-long: 8
sizeof-size_t: 8

```

When the time format is correct, the clone is successful, so this is followed by the shallow-list£º

```shell
GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=2015-10-12
```

Github Issues: https://github.com/gitgitgadget/git/issues/457

Re: Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

[Junio C Hamano]

"Force.Charlie" <force@forcemz.net> writes:

> # time format wrong
> git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012

That's the valid/right way to specify the timestamp that is
20,151,012 seconds after the epoch (i.e. 1970-01-01), isn't it?

Re: Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

[Denton Liu]

Hi Junio,

On Wed, Nov 13, 2019 at 12:42:28PM +0900, Junio C Hamano wrote:
> "Force.Charlie" <force@forcemz.net> writes:
> 
> > # time format wrong
> > git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
> 
> That's the valid/right way to specify the timestamp that is
> 20,151,012 seconds after the epoch (i.e. 1970-01-01), isn't it?

I don't think so. When we run the same thing under protocol v1, we get
the following:

	$ git -c protocol.version=1 clone https://github.com/git/git.git --shallow-since=20151012
	Cloning into 'git'...
	fatal: the remote end hung up unexpectedly

even though the following does work:

	$ git -c protocol.version=1 clone https://github.com/git/git.git --shallow-since=2015-10-12
	Cloning into 'git'...
	remote: Enumerating objects: 93982, done.
	...

which suggests to me that the non-dashed form is invalid.

Thanks,

Denton

Re: Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

[Denton Liu]

On Wed, Nov 13, 2019 at 09:00:52AM +0800, Force.Charlie wrote:
> Recently, when I tested my Git Over HTTP server, I found a bug in Git. When we used git -c protocol.version=2 clone --shallow-since , if the time format is wrong, it will cause git to wait indefinitely.
> 
> Github supports Wire Protocol to reproduce, Gitlab does not support it and does not reproduce it.
> 
> The commands that can be retried are as follows:
> 
> ```shell
> # time format wrong
> git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
> # trace
> GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
> ```
> We can see that the server closes the HTTP connection after sending the `shallow-info\n` message, and git-remote-http(s) is still waiting.
> 
> ```
> $ git --version --build-options
> git version 2.24.0
> cpu: x86_64
> no commit associated with this build
> sizeof-long: 8
> sizeof-size_t: 8
> 
> ```
> 
> When the time format is correct, the clone is successful, so this is followed by the shallow-list：
> 
> ```shell
> GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=2015-10-12
> ```
> 
> Github Issues: https://github.com/gitgitgadget/git/issues/457

FWIW, I can reproduce this issue as well. From what I can tell (without
actually looking at any code), it seems like when an invalid
`--shallow-since` is given to the server, it'll hang up on the client.

With protocol v1, the client quits as expected:

	$ git -c protocol.version=1 clone https://github.com/git/git.git --shallow-since=20151012
	Cloning into 'git'...
	fatal: the remote end hung up unexpectedly

However, with v2, I believe that the client doesn't detect the hang up
and just waits forever.

Unfortunately, I don't know the networking code at all and I don't have
time to actually dig into the code. Hopefully this helps a little bit,
though.

Thanks,

Denton